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Vitamin C for the common cold

Vitamin C is a common ingredient in many cold and flu relief products and many people take vitamin C supplements to help fight colds.

Despite huge advances in medicine to treat many conditions, the common cold still doesn’t have a cure. Antibiotics don’t work against the viruses that cause colds.

There's been controversy over vitamin C, also known as ascorbic acid, for preventing and treating the common cold for around 70 years, but what's the evidence it has any effect on the common cold?

What is vitamin C?

Vitamin C is an important vitamin and antioxidant that the body uses to keep you strong and healthy. Vitamin C is used in the maintenance of bones, muscle and blood vessels. Vitamin C also assists in the formation of collagen and helps the body to absorb iron.

Vitamin C is found naturally in vegetables and fruits, especially oranges and other citrus fruits. This key vitamin is also available as a natural dietary supplement.

Can vitamin C prevent or treat cold symptoms?

There have been many separate studies to assess vitamin C's cold fighting powers over the years giving mixed results.

One of the 'gold standards' in medical research is the overall review of all relevant, high quality studies, carried out by the UK based Cochrane Collaboration.

The trials included in the latest review, published in 2013, looked at research where at least 200mg (milligrams) of vitamin C a day was put head-to-head with a dummy pill or placebo, so adult participants didn’t know whether they were getting the vitamin or a placebo pill.

29 trials involving 11,306 people were analysed.

Taking vitamin C regularly had no effect on the numbers of most people getting colds.

However, taking vitamin C supplements at the first sign of a cold had a modest but consistent effect in reducing the duration and severity of common cold symptoms.

Five trials with 598 participants exposed to short periods of extreme physical stress, including marathon runners and skiers, found vitamin C halved the risk of getting a cold.

So overall, for most people, vitamin C won’t stop them getting a cold, but if they do get a cold, it may be slightly shorter and less severe than without the supplement.

Is vitamin C safe to take?

Taking large amounts of vitamin C a day, more than 1,000mg per day, can cause stomach pain, diarrhoea and flatulence.

Vitamin C isn't stored in the body, so people need sources of it every day. The NHS says adults need 40mg of vitamin C a day and most people can get this from a healthy balanced diet rich in fruit and vegetables.

Vitamin C supplement information

Vitamin C comes in tablets, capsules, chewables, and other forms. It is a standard ingredient in multivitamins. Doctors may sometimes give it by injection. As with any supplement, keep vitamin C supplements in a cool, dry place, away from humidity and direct sunlight.

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WebMD Medical Reference

Medically Reviewed by Dr Rob Hicks on June 28, 2017

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